The present invention relates to a stored-gas inflator for ejecting high-pressure gas filled in a pressure-resistant container through a gas outlet. In particular, the present invention relates to a stored-gas inflator including a burst shim that closes a gas outlet and an initiator that generates gas pressure to apply a pressure to the burst shim, in which the bursting pressure created by the initiator bursts the burst shim, thereby opening the gas outlet.
Stored-gas inflators mounted in automobiles are known as gas supply sources for inflating airbags to protect passengers in emergencies by ejecting high-pressure gas filled in pressure-resistant containers through gas outlets. FIG. 5 is a sectional view of such a conventional stored-gas inflator.
A stored-gas inflator 100 shown in FIG. 5 includes a pressure-resistant container 102 having a high-pressure gas charged therein. The pressure-resistant container 102 is provided with gas outlets 104 for ejecting the high-pressure gas filled in the pressure-resistant container 102 to the outside. In an ordinary state, the gas outlets 104 are hermetically sealed with a thin-plate burst shim 106 attached to an inside wall of the pressure-resistant container 102. The burst shim 106 bursts when a higher pressure (bursting pressure) than a predetermined value is applied thereto from outside, thereby causing the outlets 104 to open.
The pressure-resistant container 102 is provided with an initiator (a triggering device) 108 in the vicinity of the gas outlets 104 for applying the bursting pressure to the burst shim 106. The initiator 108 includes a base part 108a fixed to the pressure-resistant container 102 at an outer surface of the pressure-resistant container 102 and a triggering part 108b protruding from the end of the base part 108a. The triggering part 108b is triggered by a triggering signal sent from a controller (not shown).
The pressure-resistant container 102 is provided with a bursting pressure inlet 110 in the vicinity of the gas outlets 104, and the triggering part 108b is inserted in the bursting pressure inlet 110. The burst shim 106 also hermetically seals the bursting pressure inlet 110.
When a triggering signal from the controller (not shown) is sent to the initiator 108, the triggering part 108b bursts in the bursting pressure inlet 110 and applies the bursting pressure to the burst shim 106 exposed in the bursting pressure inlet 110, thereby bursting the burst shim 106, causing the gas outlets 104 to open and eject the filled gas through the outlets 104.
In the stored-gas inflator 100 described above, the burst shim 106 sealing the outlets 104 constantly receives a pressure of the charged gas from inside of the pressure-resistant container 102. On the other hand, the initiator 108 applies the bursting pressure to the burst shim 106 from the outside of the pressure-resistant container 102 where a pressure (atmospheric pressure) is significantly low as compared with the pressure of the charged gas.
Therefore, in order to burst the burst shim 106 against the gas pressure in the pressure-resistant container 102, it is necessary to apply at least twice higher pressure than the gas pressure in the pressure-resistant container 102 to the burst shim 106, so that a very high output initiator (high gas-ejection force upon triggered) is required.
Accordingly, an object of the present invention is to provide a stored-gas inflator that can eject gas with a low-output initiator.
Further objects and advantages of the invention will be apparent from the following description of the invention.
According to the present invention, a stored-gas inflator comprises a pressure-resistant container including a high-pressure-gas chamber and a gas outlet for ejecting gas from the high-pressure-gas chamber; a burst shim for sealing the gas outlet; and an initiator for generating a bursting pressure for bursting the burst shim. The stored-gas inflator also includes a duct for guiding the ejected gas from the initiator such that the burst pressure of the initiator is applied to the burst shim from the inside of the high-pressure-gas chamber.
In the stored-gas inflator of the present invention, the pressure generated by the initiator is applied to the burst shim from the inside of the gas-charged chamber via the duct. The burst shim covers and closes the gas outlet such that the burst shim is hermetically attached to the periphery of the gas outlet and constantly receives the charged-gas pressure from the inside of the gas-charged chamber. When the initiator is triggered, the ejected-gas pressure is guided through the duct and applied to the burst shim from the inside of the gas-charged chamber in cooperation with the charged-gas pressure (superimposing each other on the burst shim).
In the stored-gas inflator according to the present invention, the pressure applied to the burst shim from the inside of the gas-charged chamber is increased by the ejected-gas pressure from the initiator that is applied to the burst shim from the inside of the gas-charged chamber, thereby bursting the burst shim. Therefore, the initiator used in the stored-gas inflator according to the present invention is required to have an output for increasing the pressure applied to the burst shim from the inside of the gas-charged chamber only by a difference of the charged-gas pressure of the gas-charged chamber and the bursting pressure. Therefore, a relatively low-output initiator can easily burst the burst shim and open the gas outlet.
In the stored-gas inflator according to the present invention, it is preferable that an end of the duct faces the burst shim and the end of the duct is sealed with a sealing plate. The sealing plate and the burst shim may be connected to each other.
In the configuration described above, the burst shim closes the gas outlet such that the burst shim is attached to the periphery of the outlet and is connected to or supported by the duct at the end thereof via the sealing plate of the duct. Therefore, at the burst shim, the charged-gas pressure applied thereto from the inside of the gas-charged chamber is divided between a portion connected to the periphery of the outlet and a portion connected to the end of the duct.
The ejected-gas pressure from the initiator is applied to the sealing plate at the end of the duct. When the ejected-gas pressure breaks the sealing plate at the end of the duct, the connection between the burst shim and the periphery of the outlet can not support the charged-gas pressure in the gas-charged chamber and the ejected-gas pressure from the initiator, thereby breaking the burst shim and opening the outlet.